On what does the size of fragments made by a restriction enzyme depend?

Correct answer: On the positions of cut sites

The governing concept is restriction mapping: fragment length is determined by the distance between successive cleavage sites on the DNA molecule. If a linear DNA molecule is cut at positions measured along its length, each interval between adjacent sites becomes one fragment; the fragment sizes therefore add up to the length of the original molecule. For circular DNA, the cuts similarly define segments around the circle, with the number and arrangement of sites determining the products. Option B is correct. Enzyme taste, water smell, and tube material do not determine sequence-specific cleavage distances under a controlled reaction. Reaction conditions can affect whether digestion is complete, but they do not replace the basic rule that the locations of recognition and cut sites establish fragment size.